Liquid crystal displays (LCD) have been widely applied in electrical products due to the rapid progress of optical and semiconductor technologies. Moreover, with their advantages of high image quality, compact size, light weight, low driving voltage and low power consumption, LCDs have been introduced into portable computers, personal digital assistants and color televisions and are becoming the mainstream display apparatus.
In liquid crystal displays, a source driver is used to convert a digital signal to an analog voltage to transmit the image signal to the display, so it is also called the data driver. To orderly pass the signals, the source driver comprises a shift register circuit composed of a plurality of shift register units electrically connected in series. The shift register circuit can output an enable signal to enable the digital image signals to orderly load into a corresponding latch. Then, the digital image signals are sent to a digital-to-analog converting circuit from the latch to convert them into analog driving signals to drive the liquid crystal display.
In a conventional shift register circuit, after the shift register circuit is produced, if part of the unused shift register units are to be disabled in multi-channel mode, the unused shift register units need to be bypassed one-by-one with jump lines. This not only increases the size of the chip but also results in late delivery of product when the specification required by customers is not made yet or the specification is altered temporarily.